The pan-European STOXX 600 was down 0.7% at closing, France's CAC 40 fell 1.4% after a auto hit a group of soldiers in Paris in what is thought to have been a deliberate act, and a fall in bond yields saw Germany's DAX down 1.1%.
THE QUOTE: While the tough talk about the potential for war is scary, investors have heard it many times before. The stock fell $166 to $1,882.94.
Instead, investors headed for safe havens, such as gold, which gained as much as 1.2% - a near two-month high - in Wednesday trading. The stock lost $5.23 to $101.75.
Revenues in the first six months of the year rose 5.6% to 3.21bn euros (£2.9bn), helped by June's hot weather, and operating profits jumped almost 21% to 266.4m euros.
"Trump has upped the ante so the market is having to price in possible military intervention", said Jasper Lawler, head of research, at London Capital Group, in a note.More news: Apple may drop the S from the iPhone
Worldpay Group PLC (LON:WPG) added to gains, as shares rallied 1.34%, still supported by news on Wednesday that USA credit card processing company Vantiv agreed to buy the British group for £8 billion. Benchmark U.S. crude fell 83 cents, or 1.7 percent, to $48.73 a barrel on the New York Mercantile Exchange. It was up $15.70, or 1.2 percent, to $1,278.30 an ounce. European markets were also struggling amid the simmering political stand-off, with the Cac 40 in France dropping 1.4% and Germany's Dax tumbling by 1.1%. Humana rose $3.59, or 1.4 percent, to $253.81.
The biggest risers on the FTSE 100 Index were Smurfit Kappa up 38p to 2,224p, Persimmon up 39p to 2,501p, DCC up 70p to 6,885p, Barratt Developments up 6p to 595.5p.
Gold miners Randgold Resources (RRS.L) and Fresnillo (FRES.L) were among the only gainers on the FTSE .FTSE, up 2.8 to 4.9 percent as investors rushed to the safety of gold. Brent crude, used to price global oils, declined 23 cents to $51.67 per barrel in London. Copper fell 2 cents to $2.93 a pound.
Hong Kong shed more than one percent and Shanghai also closed down, while Seoul shares continued their sell-off after slumping Wednesday, with the won again softening. Wholesale gasoline was little changed at $1.62 a gallon, heating oil rose 2 cents to $1.65 a gallon and natural gas rose 6 cents to $2.88 per 1,000 cubic feet.
But losses soon resumed, with Tokyo edging down as the Nikkei again came under pressure from the strength of the safe-haven yen, which hit eight-week highs Wednesday against the dollar. The euro strengthened to $1.1756 from $1.1752.